<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Modal Dialog</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            background-color: #f0f2f5;
            display: flex;
            justify-content: center;
            align-items: center;
            height: 100vh;
        }
        .modal {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0, 0, 0, 0.5);
            justify-content: center;
            align-items: center;
        }
        .modal-content {
            background-color: white;
            padding: 20px;
            border-radius: 8px;
            width: 300px;
            text-align: center;
        }
        .modal-content button {
            padding: 10px 20px;
            border: none;
            border-radius: 5px;
            background-color: #007bff;
            color: white;
            font-size: 1em;
            cursor: pointer;
        }
        .modal-content button:hover {
            background-color: #0056b3;
        }
    </style>
</head>
<body>
    <button onclick="openModal()">Open Modal</button>

    <div id="myModal" class="modal">
        <div class="modal-content">
            <h2>Modal Title</h2>
            <p>This is a simple modal dialog.</p>
            <button onclick="closeModal()">Close</button>
        </div>
    </div>

    <script>
        function openModal() {
            document.getElementById('myModal').style.display = 'flex';
        }

        function closeModal() {
            document.getElementById('myModal').style.display = 'none';
        }
    </script>
</body>
</html>